Thin film magnetic recording heads are used in the data storage industry for recording data onto narrow tracks on a magnetic medium, such as a hard disk drive platter. FIG. 1 shows a simplified cross sectional view of an exemplary recording head. The recording head 100 includes two conductive layers 101 and 103, called poles, separated by an insulating layer 105. The poles are conductively connected at one end 107 and are separated by a thin non-magnetic gap layer 102 at another end 108 so that the overall configuration of the connected conductive layers 102 and 103 has a somewhat horseshoe-like shape. Conductive wires 104 are embedded within the insulating layer 105 to form a conductive coil. During a write operation a magnetic flux 106 is induced in the poles by an electrical current flowing through the coils 104. This magnetic flux 106 protrudes at a discontinuity caused by the thin non-magnetic insulating layer 102. The protruding flux may be used to write data on a disk surface.
After data is written to a magnetic medium using a recording head, the data may be read from the medium using a read sensor. Some types of recording heads can operate as read sensors. However, a separate read-only sensor, such as a spin-valve sensor, can often provide improved read sensitivity. A spin valve sensors detects magnetically recorded data based on a change in resistance attributed to a magnetic spin-dependent transmission of conduction electrons between a free magnetic layer and one or more pinned magnetic layers through non-magnetic layers. FIG. 2 shows a simplified cross sectional view of a dual spin valve sensor. The sensor 200 includes a free magnetic layer 211 sandwiched between nonmagnetic layers 212 and 215 which, in turn, are sandwiched between pinned magnetic layers 213 and 216. The pinned magnetic layers 213 and 216 have a fixed magnetic direction set by pinning layers 214 and 217. Pinning layers 214 and 217 may be formed from a hard magnetic material (i.e., a material having a fixed magnetic direction) or may be exchange tabs in contact with surfaces of the layers 213 and 216. Single spin valve sensors may include layers 211-214 and omit layers 215-217.
Recording heads and read sensors can be isolated from each other using magnetic and dielectric layers. The magnetic and dielectric layers provide electrical and magnetic interference protection and can also provide corrosion resistance and other desired properties. As head geometries decrease, greater challenges are faced in forming thin and reliable magnetic and dielectric layers. Among the challenges faced are forming a dielectric gap with a high breakdown and low leakage current to provide effective isolation between the write head and read sensor stack. Consequently, improved dielectric gaps for use in thin film heads, and means to form such gaps, are desired.
In general, in one aspect, the invention features a data transfer head. The head includes a data transfer element for transferring date between the data transfer head and a data storage medium and a dielectric gap electrically shielding the data transfer element. The dielectric gap includes a plurality of layered dielectric film wherein adjacent dielectric films are formed of different dielectric materials.
Implementations may include one or more of the following features. The first and second dielectric materials may each have a thickness of less than one micron between their first and second opposing surfaces. A surface of one of the dielectric films may be adjacent to a surface of the data transfer element. Different dielectric layers formed of the same dielectric material may be separated along at least a subsection by a different dielectric material. The different dielectric materials may be selected from the group consisting of A2O3, Si3N4, SiC, SiO2, AlN, Ta2O5, TiO2, BN, and diamond-like carbon. The data transfer element may be, e.g., a spin valve or other read sensor or a write head and the data transfer head can include both a read sensor and a write head separated by the dielectric gap.
In general, in another aspect, the invention features a method of forming a magnetoresistive sensor. The method includes forming a thin film data transfer element and forming a dielectric gap to electrically shield the data transfer element. Forming the dielectric gap includes depositing a number of adjacent dielectric films on an underlayer and depositing a second dielectric film on the first dielectric film. The second dielectric film being different from the first dielectric film.
Implementations may include one or more of the following features. Additional dielectric films may be deposited to form the dielectric gap. For example, a third dielectric film can be deposited over the second dielectric film. The first and third dielectric films may be of the same material and may be separated from each other by the second dielectric film which is of a different dielectric material. Forming the thin film data transfer element may include forming a magnetic read sensor and/or a write head and forming the dielectric gap may include forming the dielectric gap between a read sensor and a write head.
Implementations may include one or more of the following advantages. A multi-layer dielectric can be used to provide a dielectric gap having opposing surfaces with different bonding and adhesion characteristics. The opposing surfaces may be formed of different materials selected to provide good adhesion to adjacent surfaces of other layers. A dielectric may exhibit improved corrosion resistance, increased breakdown voltage, and/or decreased leakage current.